This invention relates generally to packaging and specifically to hermetically heat sealable, easy open, heat-shrinkable packaging for food products.
It is common practice to package articles such as food products in thermoplastic films or laminates to protect the product to be packaged from abuse and exterior contamination and to provide a convenient and durable package for transportation and sale to the end user. Shrink packaging of food products has become extensively used due to its many advantageous properties, e.g., strength, compactness, content security, purge resistance, the attractive appearance of the packed article, etc., which add to the commodity value of the packaged article. Shrink packaging refers to the use of a packaging film manufactured in such a way that when it is exposed to a certain amount of heat, the film will contract in at least one direction along its length or width, preferably in both directions, reducing its overall surface area. When articles are packaged in this type of film, air in the package is usually evacuated and the package is typically passed through a heated shrink tunnel where the package is exposed to an elevated temperature which causes the film to react to the heat and contract around the object. This process results in an attractive skin-tight package. Articles packaged using shrink packaging are numerous and can include food articles, such as frozen pizzas, cheese, poultry, fresh red meat, and processed meat products as well as nonfood industrial articles such as wooden blinds, CD's, etc.
Many food products, such as poultry, fresh red meat, cheeses, and processed meat products, are packaged in individual, pre-manufactured bags of heat-shrinkable film. Typically, individual bags or pouches for packaging food articles include one to three sides heat sealed by the bag manufacturer leaving one side open to allow product insertion and a final seal performed by the food processor. Such individual bags are typically manufactured from shrink films by producing a seamless tube of heat-shrinkable film having a desired diameter, heat sealing one end of a length of the tubular film and cutting off the tube portion containing the sealed portion, thereby forming an individual bag. The bag formed thereby, when it is laid flat, has a bottom edge formed by the heat seal, an open mouth opposite the sealed bottom and two seamless side edges formed by the fold produced when the tube is laid flat. Another method of forming bags from a seamless tube comprises making two spaced-apart transverse seals across the tube and cutting open the side of the tube. If flat sheets of film are used, bags are formed therefrom by heat sealing three edges of two superimposed sheets of film or by end-folding a flat sheet and sealing two sides. U.S. patents describing known heat shrinkable bags include U.S. Pat. Nos. 6,511,688, 5,928,740, and 6,015,235. U.S. patent application Ser. No. 10/371,950, in the name of Thomas Schell et al., filed on Feb. 20, 2003, entitled “HEAT-SHRINKABLE PACKAGING RECEPTACLE”, the entirety of which is hereby incorporated by reference hereto, discloses individual heat-shrinkable bags formed from a sheet of film, preferably in a continuous process, wherein opposing side edges of the sheet are sealed longitudinally to form a tube member, which is then sealed and cut transversely to close an end of the tube member thereby forming a backseamed bag.
The known bags for heat-shrink packaging include strong factory and final closing seals to prevent the heat sealed seams from pulling apart during the heat shrinking operation, or during the handling and transport of the packaged article. Although the strong heat seals provide protection against unwanted seal failure, such seals also make it difficult for the end user to open the package. Accordingly, there is needed an improved heat-shrinkable packaging receptacle that includes seals of sufficient seal strength to survive the heat shrinking process and handling and resist spontaneous opening due to residual shrink forces, yet includes at least one heat seal that is readily openable by application of force without requiring use of a knife or cutting implement and without uncontrolled or random tearing or rupturing of the packaging materials, e.g., away from the seal area, which may result in opening in undesired location or in sudden destruction of the package and inadvertent contamination or spillage of the contents of the package.